R. Maccaferri

The antiproton decelerator: AD

A simplified scheme for the provision of antiprotons at 100 MeV/c based on fast extraction is described. The scheme uses the existing p~ production target area and the modified Antiproton Collector Ring in their current location. The physics programme is largely based on capturing and storing antiprotons in Penning traps for the production and spectroscopy of antihydrogen. The machine modifications necessary to deliver batches of 1/spl times/10/sup 7/ p~/min at 100 MeV/c are described. Details of the machine layout and the experimental area in the existing AAC Hall are given.

The Antiproton Decelerator: AD

Abstract In view of a possible future programme of physics with low-energy antiprotons, a simplified scheme for the provision of antiprotons at 100 MeV/ c has been studied. It uses the present target area and the modified Antiproton Collector (AC) in its present location. In this report the modifications and the operation are discussed.

Status of the antiproton decelerator: AD

A simplified scheme for the provision of antiprotons at 100 MeV/c in fast extraction is described. The scheme uses the existing p production target area and the modified Antiproton Collector Ring in their current location. Some modifications necessary to deliver batches of 1 × 10 7 antiprotons every minute at 100 MeV/c are described, details of the machine layout and the experimental area in the existing AAC Hall are given.

Active methods of instability suppression in a neutralized electron beam

Abstract A large space-charge is detrimental to the cooling process of a dense beam. Generation of a neutralised electron beam is restricted by beam-drift instability. To suppress this instability, active methods are used: a kicker with a transverse electric field (shaker) and longitudinal electrodes placed in the vacuum chamber and in the gun region expel secondary electrons. Results of experiments dedicated to the development of beam stabilisation on the JINR test bench and in the electron cooling system at LEAR are discussed.

TRANSVERSE PROFILE MONITOR USING ION PROBE BEAMS

A profile monitor is described that makes use of a low-intensity and low-energy ion beam to measure the transverse profile of a dense proton beam of small dimensions. Three techniques are considered based on the use of ion beams having a pencil, curtain, or cylindrical shape. The detector is almost non-interceptive for the proton beam and does not introduce disturbances in the machine environment. The theoretical aspects of the techniques used, together with experimental results obtained at the CERN SPS and Linac, are presented.

RECENT RESULTS ON LEAD-ION ACCUMULATION IN LEAR FOR THE LHC

Abstract To prepare dense bunches of lead ions for the LHC it has been proposed to accumulate the 4.2 MeV/u linac beam in a storage ring with electron cooling. A series of experiments is being performed in the low-energy ring LEAR to test this technique. First results were already reported at the Beam Crystallisation Workshop in Erice in November 1995. Two more recent runs to complement these investigations were concerned with: further study of the beam lifetime; the dependence of the cooling time on optical settings of the storage ring and on neutralization of the electron beam; and tests in view of multiturn injection. New results obtained in these two runs in December 1995 and in April 1996 will be discussed in this contribution.

Recent lead ion storage tests on LEAR

With the completion of the antiproton physics program, the Low Energy Antiproton Ring is now available to be used as an accumulator ring for heavy ions in the LBC injector chain. The proposed scheme for the injection of Pb ions is given, where an intensity gain of 125 is obtained by accumulating Pb ions with electron cooling in the LEAR ring. With a linac cycling at 10 Hz and cooling times faster than 100 ms, 20 pulses can be accumulated in 2 s before transfer to the PS, the next machine in the chain. A number of machine experiments have been performed and will continue this year, in order to establish the techniques required. We discuss injection line tests, ion beam lifetime and vacuum measurements and cooling time measurements.

EXPERIMENTAL STUDIES OF ELECTRON BEAM NEUTRALISATION

Abstract This report presents results of experiments performed between 1994 and 1996 by a CERN/JINR collaboration, aimed to study the problem of the generation of intense electron beams whose space charge is neutralised by the residual gas ions. The problem is related to the development of electron cooling methods. The large space charge potential for high density electron beams is a significant drawback for the cooling process. In order to reduce this effect, an electron beam neutralisation system has been implemented on the LEAR cooler and the JINR test bench. In this paper we briefly discuss the physics of the neutralisation process, technological aspects of neutralisation, the measurement techniques and the results.

Neutralisation of the LEAR electron-cooling beam: experimental results

The LEAR electron cooler uses dense electron beams. Because of this high density the large space-charge potential induces significant drawbacks for the cooling process itself. As a consequence a space-charge neutralisation system has been implemented on the cooler. It consists of two positively polarised pairs of electrodes, placed on the outside of the drift space, which aim to store the ionised positive ions of charge Z. The major difficulty arises in the neutralisation instabilities. This paper reports on the technological aspects, the measurement techniques and the results.

An inexpensive analog function generator in VME standard

Abstract As part of the rejuvenation of the CERN accelerators control system, a simplified analog function generator has been developed in the VME standard, replacing the 15 years old ones. In order to be usable for all CERN configurations, it is split in two parts. The part in the VME module generates the function in digital form and the digital values are transmitted in realtime over a serial link to a DAC module that generates the actual analog function. The DAC is very simple and presently exists in VME, G64 and single Europe standard. It can easily be implemented in any other standard, thus allowing adaptation to all existing configurations where a function generator is needed. The analog function is approximated by vectors; up to 512 vectors can be used per function and up to 32 functions can be stored for each function generator at one time. Each vector is approximated by a staircase function with 5 μs step size or a multiple of it.